Pdf "could not be saved" because "the file is locked" (not locked) or "you don't have permission" (I created the file)

Whether I use Preview or Adobe Acrobat Reader, I cannot save or autosave any highlights, notes or other edits to any pdf file on my MacOS Sonoma 14.2.1. The message varies between "the file is locked", "you don't have permission" or "you don't have permission to save to this location". However, when navigating to the file > 'get info', I can see that all users are set to "read & write" permissions including myself and that the checkbox for locked files is not checked. Additionally, Preview and Adobe Acrobat Reader both have full disk access to my Mac so should have no issue saving to any location. My Macintosh HD disk is on my desktop as it has been for a while - could that be the problem? If anyone has any idea what could be wrong, I would really appreciate it. Thank you